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4.6 External Trigger
An external trigger is an event that starts an exposure. The trigger signal is either generated
on the frame grabber (soft-trigger) or comes from an external device such as a light barrier. If a
trigger signal is applied to the camera before the earliest time for the next trigger, this trigger
will be ignored. The camera property
Counter.MissedTrigger
stores the number of trigger
events which where ignored.
4.6.1 Trigger Source
The trigger signal can be configured to be active high or active low. One of the following
trigger sources can be used:
Interface Trigger In the interface trigger mode, the trigger signal is applied to the camera by
the CameraLink interface.
I/O Trigger
In the I/O trigger mode, the trigger signal is applied directly to the camera by the
power supply connector (over an optocoupler).
I n t e r f a c e T r i g g e r
D A T A
C a m e r a
o p t o
I / O
C L
F r a m e g r a b b e r
A n y T r i g g e r
S o u r c e
I / O T r i g g e r
A n y T r i g g e r
S o u r c e
Figure 4.22: Trigger Inputs
4.6.2 Trigger Mode
Depending on the trigger mode, the exposure time can be determined either by the camera or
by the trigger signal itself:
Camera-controlled Exposure In this trigger mode the exposure time is defined by the camera.
For an active high trigger signal, the camera starts the exposure with a positive trigger
edge and stops it when the preprogrammed exposure time has elapsed. The exposure
time is defined by the software.
Level-controlled Exposure In this trigger mode the exposure time is defined by the pulse width
of the trigger pulse. For an active high trigger signal, the camera starts the exposure with
the positive edge of the trigger signal and stops it with the negative edge.
Level-controlled Exposure is not available in simultaneous readout mode.
Figure 4.23 gives an overview over the available trigger modes. The signal ExSync stands for the
trigger signal, which is provided either through the interface or the I/O trigger. For more
information and the respective timing diagrams see Section 5.4
4.6 External Trigger 37